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    • ▾1st grade
      • ▸Place value
        • •Count and write numbers within 120
        • •Skip count by 3s and 4s
        • •Place value with tens
        • •Compare two-digit numbers
      • ▾Addition and subtraction
        • •River crossing puzzles
        • •Add and subtract within 20
        • •Add within 20, word problems involving three addends
        • •Use one addition problem to solve another
        • •Add by making tens
        • •Subtract by adding
        • •Understand the equals sign
        • •Add and subtract within 20, missing number problems
        • •Add and subtract within 20, word problems
        • •Add within 100, concrete and pictorial
        • •10 more or 10 less
        • •Subtract multiples of ten from multiples of ten
      • ▸Measurement, data, and geometry
        • •Order without tools
        • •Measure given a unit
        • •Bar and picture graphs having three categories of data
        • •Tell and write time, hour and half-hours
        • •Definitions of shapes
        • •Compose 2D and 3D shapes
        • •Halves and quarters
     › 1st grade › Addition and subtraction

    Add by making tens

    Add using the make tens strategy. We can start with Unifix cubes, if necessary. For example, lay out Unifix cubes of length 2, 6, and 4. The student should recognize that 6 + 4 = 10, and from their work with teen numbers in Kindergarten, recognize that 10 + 2 = 12. Then we remove the Unifix cubes and ask the same question. Students are expected to say something like, 6 and 4 is 10, and I know 10 and 2 is 12, so the answer is 12.

    Conclude by leading this investigation:

    Speed Counting to Infinity
    by MathPickle

    1.OA.B.3: Apply properties of operations as strategies to add and subtract. Students need not use formal terms for these properties. Examples: If 8 + 3 = 11 is known, then 3 + 8 = 11 is also known. (Commutative property of addition.) To add 2 + 6 + 4, the second two numbers can be added to make a ten, so 2 + 6 + 4 = 2 + 10 = 12. (Associative property of addition.)